Positive-displacement pump for metering fluids



June 4, 1968 H. c. DREHER 3,386,383

POSITIVE-DISPLACEMENT PUMP FOR METERING FLUIDS Filed Nov. 9, 1966 INVENTOR.

HANS 0. DREHER BY Mm AGENT United States Patent 3,386,383 POSITIVE-DISPLACEMENT PUMP FOR METERING v FLUIDS Hans C. Dreher, Dallas, Pa., assignor to General Cigar Co., Inc., New York, N.Y., a corporation of New York Filed Nov. 9, 1966, Ser. No. 593,010 2 Claims. (Cl. 103-38) ABSTRACT OF THE DISCLOSURE Background of invention Compared with the pump of the present invention, all of the prior devices have one or more of the following limitations or disadvantages: (a) the pump will not operate correctly in all positions such as when device is held vertically instead of horizontally; '(b) the pump is designed to operate only at atmospheric pressure; (0) the pump is designed to operate with the fluid reservoir located above the discharge spout; (d) the pump allows air to mix with the liquid being dispensed; and (e) the pump is manually operated and therefore the volume of liquid dispensed per stroke is not constant. Contrarily, the present pump operates properly: (a) irrespective of its position or orientation; (b) in any atmospheric environment including a vacuum; (c) irrespective of the position of the fluid reservoir; ((1) without mixing aid with the liquid being dispensed; and (e) automatically controlled to dispense accurately and repeatedly a desired volume. In addition, the present pump is infinitely variable between a very minute amount and the maximum capacity of the pump.

Description of invention It is an object of the invention to provide a positivedisplacement pump which accurately meters controlled amounts of pressurized fluids. A further object is to provide a common source of gas pressure both to operate the pump mechanism and to feed the liquid to the pump. Another object is to provide a pump that will operate on pumpable liquids of a wide range of viscosities in any desired amount independent of the pump position.

The pump construction has (a) a central section having a bore along its length with inlet and outlet ports communicating with the bore near its opposite ends, a main piston with a shaft projecting from its compression end and a secondary piston in the form of a ring slidably mounted on the shaft and both pistons being slidably operable within the bore; (b) a housing attached near the outlet port on the central section to provide both a fixed stop and an adjustable stop to limit the strokes of the secondary and main pistons, respectively; and (c) drive means for the pump, preferably an air cylinder located on the opposite end of the central section with a separate piston aligned with and attached to the main piston to-actuate the dispensing pistons within the central section of the pump.

Patented-June 4, 1968 ice Since many liquids corrode common metals, the pump may be constructed of stainless steel or other non-corrodible materials to increase its life and to guard against contamination of the liquid being dispensed. The pump is particularly useful in dispensing fairly viscous fluids such 'as pastes or gelatinous materials. For positive feeding of viscous liquids, it is preferred to use pressurized gas over the liquid in a closed reservoir. However, a liquid of low viscosity could be fed to the pump by gravity from a suitably positioned reservoir.

For a better understanding of the invention, reference is now made to the accompanying drawing which is a sectional elevation of a preferred embodiment of the pump of this invention.

Pump 2 comprises cylindrical housing 4 having elongated bore 6 along its axis. Slidably operable within bore 6 is main piston 8 having elongated shaft 10 extending from its compression end. Secondary piston 12 in the form of a ring or sleeve is slidably mounted on the free end of shaft 10 for movement on shaft 10 within bore 6. Compression spring 14 also mounted on shaft 10 between the compression end of main piston 8 and secondary piston 12 flexibly holds secondary piston 12 against retainer 16 on the free end of shaft 10. Main piston 8 and secondary piston 12 have pairs of peripheral grooves 18 and 19, respectively, to accommodate piston rings or O-rings 20 and 21 which serve as both seals and bearing surfaces between the respective pistons and bore 6. Secondary piston 12 has inner groove 22 on its inner surface to hold O-ring or piston ring 24 which serves as a seal and bearing surface between shaft 10 and secondary piston 12. Inlet port 26 admits a pressurized fluid into bore 6 through orifice 28 which is located close to the compression end of main piston 8 when positioned at the start of the compression stroke. The pressurized fluid is dispensed from bore 6 through orifice 30 past one-way ball valve 32 and outlet port 34 after secondary piston 12 has moved past orifice 30 during the forward or compression stroke of main piston 8. Actually, no fluid is pumped until secondary piston 12 hits its stop at shoulder 52 and at the same time main piston 8 continues its travel. The amount of over-travel of main piston 8 until it is stopped by adjustable screw 56 determines the amount of liquid forced out through outlet 34. Orifice 30 is sealed by the side of secondary piston 12 when pressurized fluid is charged into bore 6 through orifice 28. As main piston 8 moves forward orifice 28 is sealed by the side of main piston 8 and as the pressurized fluid is pushed ahead by the compression end of main piston 8, orifice 30 simultaneously is uncovered or opened to permit the discharge of the fluid as the side of secondary piston 12 moves past orifice 30. On the return stroke, outlet orifice 30 is again covered or sealed by secondary piston 12 and inlet orifice 28 is uncovered or opened for a new charge of the pressurized fluid. Thus, only a controlled amount of the fluid will be discharged on any given forward stroke and no excess can be dispensed because the inlet is sealed immediately after the charge and the outlet is sealed immediately after the discharge.

Means may be provided to bleed air fro-m the pump before a liquid is charged to the pump. Such air bleed-off may be achieved with valve step 36 and steel ball 42 disposed in cylindrical housing 4 between inlet port 26 and outlet port 34-; bleed-off orifice 38 communicates with bore 6 near the trailing end of secondary piston 12 when it is disposed at the start of the compression stroke. Hardened stainless steel ball 42 closes orifice 38 when valve stem 36 is turned down tight. Bore 40 connects orifice 38 with outlet 34 so that when valve stem 36 is turned up entrapped air followed by liquid from orifice 38 flows through bore 40 to outlet 34. In short, with pump pistons 8 and 12 in the charge position, turning up valve stem 36 to the open position allows pressurized liquid entering bore 6 through orifice 28 to bleed air from the pump through orifice 38, bore 4t} and outlet port 34.

Cylinder cover 44 with gasket 46 is attached to the outlet end of housing 4 by screws (not shown). Bore S of reduced diameter extending partially through cover 44 along its central axis aligns with bore 6 of housing 4 and forms shoulder 52 which acts as a stop to the movement of secondary piston 12. The length of secondary piston 12 is not greater than the distance between shoulder 52 and the edge of orifice 30. During the forward stroke the outer face of secondary piston 12 comes into contact with shoulder 52 and the inner face of piston 12 is then just past orifice 30 thus forming an end wall of bore 6. Threaded hole 54 is aligned to communicate with bore 50 and holds adjustable screw 56 which acts as stop for shaft to provide an adjustable limit for the stroke of main piston 8. The setting of screw 56 determines the amount of forward stroke of main piston 8 after secondary piston 12 has been stopped by shoulder 52 thereby controlling the amount of pressurized fluid dispensed from bore 6 through orifice 30.

An air-actuating mechanism attached on the inlet end of cylindrical housing 4 comprises cylinder 60 capped by cylinder cover 62 both of which are held firmly against cylindrical housing 4 by screws (not shown). Circular groove 66 on the end of housing 4 is fitted with O-ring 68 as gasket between cylinder 60 and housing 4. Similarly, cylinder 60 contains groove 70 to accommodate O-ring 72 as gasket between cylinder 60 and cylinder cover 62. Piston 74 has piston ring or O-ring 76 circumferentially fitted in a peripheral groove and is slidable within cylinder 60. The free end of piston 8 which extends from bore 6 through cylinder 60 has piston 74 attached thereto by screw 78. Compressed air is charged into the actuating mechanism through inlet port 80 to circular antecham'ber 82 in the inner face of cylinder cover 62. Piston 74 is forced forward in cylinder 60 which in turn pushes main piston 8 of the pump. As main piston 8 moves forward, orifice 28 is closed and simultaneously orifice 30 is opened. The pressurized fluid already within bore 6 is pushed forward and dispensed through orifice 30 after secondary piston 12 has been stopped by shoulder 52. The amountof fluid forced out through orifice 30 is related to the amount of over-travel of main piston 8 after secondary piston 12 has been stopped by shoulder 52. To actuate the return stroke, pressurized air enters port 84 at the inlet end of housing 4 and flows through orifice 86 to circular afterchamber 88 in the face of housing 4 opposite the forward end of piston 74 and forces piston 74 to make its return stroke as well as that of piston 8. When retainer 16 again contacts secondary piston 12 during the return stroke of piston 8, piston 12 also executes its return stroke thereby sealing orifice 30. At the end of the return stroke, orifice 28 is again opened because main piston 8 has moved past this orifice. Thus, a fresh charge of pressurized fluid is admitted through orifice 28-into the annular space between bore 6 and shaft 10, the length of the annular space being the distance =between'the compression face of main piston 8 and the trailing face of secondary piston 12 when the latter abuts retainer 16.

For the reciprocating action of the air-actuating mechanism, it is obvious that ports 86 and 84 must alternately act to charge pressurized air into and exhaust pressurized air from antechamber 82 and afterchamber 88, respectively, of cylinder 60. On the forward stroke of all the pistons 74, 8 and 12, pressurized air is charged into antechamber 82 from port 80 while air is simultaneously exhausted from afterchamber 88 through port 84. On the return stroke of pistons 74, 8 and 12, pressurized air is charged into afterchamber 88 through port 84 while air is simultaneously exhausted from antechamber 8 through port 80.

A typical installation and operation of the pump of this invention has been described in applicants copending application Ser. No. 593,609, filed of even date herewith. FIGURE 3 of the copending application shows that compressed air flows from a regulator at a pressure of about 40 pounds per square inch to a supply port of a four-way solenoid valve which has two of its other ports connected to the two ports of the air-actuating mechanism of the pump of this invention. In the present application, ports and 84 would be so connected to two of the ports of the four-Way solenoid valve; the remaining port of the solenoid valve is for venting air from cylinder 60. Hence, in one of the two positions of the four-way solenoid valve, the compressed air enters the valve through the supply port and flows through the port connected to port 80 of cylinder 60 while air in cylinder 66 escapes through port 84 which is connected to another port of the valve that is then in communication with the venting port of the valve. In the other position of four-way solenoid valve, the compressed air from the supply port flows to the port connected to port 84 while air in cylinder 60 passes through port 80 to the connecting port of the valve which is then in communication with the venting port.

FIGURE 3 of the copending application also shows that compressed air from the same source used to operate the air-actuating mechanism of the pump of this invention may be used to pressurize a liquid in a closed vessel that is connected by a pipe extending from the liquid reservoir in the closed vessel to the inlet port of the pump, herein designated as port 26.

As already pointed out, a feature of the pump of the invention is the large variation that may be made at will in the amount of fluid discharged per compression stroke of the pump. The amount discharged may be infinitely reduced from the full design capacity of the pump to the minutest desired amount such as 0.01 cubic centimeter. It is also well to note that the pump can handle highly viscous liquids and emulsions as well as fluids of low viscosity.

Those skilled in the art will readily visualize changes and modifications that may be made in the embodiment of the invention described and illustrated without departing from the spirit and scope of the invention. Hence, the claims should not be interpreted in any restrictive sense other than that imposed by the limitations recited within the claims.

What is claimed is:

1. A positivedisplacement pump for metering fluids which comprises:

(a) a pump housing having an elongated bore;

(b) an inlet and an outlet communicating through said housing with said bore, respectively, near opposite ends of said housing for charging a fluid into, and dispensing said fluid from said bore;

(0) a main piston having a coaxial shaft of reduced diameter extending from the compression face of said main piston which is slidably operable within said bore;

(d) a secondary piston in the form of a ring being slid ably operable on said shaft and within said here;

(e) a retainer on the free end of said shaft to keep said secondary piston on said shaft;

(f) stop means on the outlet end of said housing to limit the stroke of said secondary piston; and

(g) an adjustable member on said outlet end of said housing aligned with said free end of said shaft so as to be contacted thereby and thus limit the compression stroke of said main piston;

the relative positions of said pistons within said bore being such that at the start of said compression stroke said main piston leaves said inlet open while said secondary piston keeps said outlet closed and during said compression stroke said main piston closes said inlet while said secondary piston opens said outlet.

2. The pump of claim 1 wherein a compression spring 5 6 is mounted around the coaxial shaft between the main 2,955,539 10/1960 Gardner 103-38 and secondary pistons to hold them flexibly apart. 3,011,451 12/ 1961 Griffin 103-166 3,250,247 5/1966 Beaman 103-88 References Cited UNITED STATES PATENTS 2,517,952 8/1950 Welling 103-166 2,817,417 12/1957 Cunningham 10337 5 DONLEY J. STOCKING, Primary Examiner.

LAURENCE V. EFNER, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,386,383 June 4, 1968 Hans C. Dreher It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 41, "aid" should read air Column ;Z 11ne 62, "step" should read stem Column 3, line 73, 8 should read 82 Column 4, line 2, "593,609" should read 593,069

Signed and sealed this 14th day of October 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

